The objectives of this proposal are (1) a genetic analysis of meiotic mutants which act in male Drosophila melanogaster and (2) the identification and localization of those regions of the chromosome that are important in chromosome pairing and disjunction. This latter objective will be achieved through the analysis of the segregational patterns of various rearranged chromosomes, including inversions, translocations, compound autosomes, and Free-2-left, Free-2-right chromosomes. The genetic control of meiosis is different for the two sexes. We believe that the two systems evolved from a common, primative system, and therefore, should have certain fundamental similarities. Three such possible similarities have been found.